There's a reason things like the Geek Squad are around and can charge as much as they do...
But the truth is, replacing a cylinder in a car is so much harder than reading and following these instructions, and even if you don't understand either task the car cylinder task takes longer, requires more tools, makes a mess, etc.
An average person who has no intuition for passwords could just turn their router off when they aren't using it.
The variance in technical ability of the 'average person' nowadays is pretty wide. There are still pop-up clicking grandmothers on IE7 out there, but there are also plenty of baby-boomers with the ability to set the clock on their VCR's, which is a much more fair analogy to the task of router configuration.
I think the important thing is getting the message out that such configuration is much more important than having the clock on your VCR right, which is probably how important the average person thinks router configuration is. As you said in another comment, routers are effectively shipping to average people broken. I think if this were more commonly known, people would take the time to learn and configure their networks. Not ALL people, but more average people than do today. The real problem is not that people are not technically capable of doing the task, but they do not know that it is a task that is really necessary; it's not common knowledge that a brand new router is a security risk.